The more regulatory competence and authority is conferred upon larger institutions and systems of governance—especially at the global level—the more we will be confronted with questions of how to ensure the accountability and legitimacy of governance. Simply put, we are faced with the need to understand the democratic quality of earth system governance. What are the sources of accountability and legitimacy in earth system governance? What are the effects of different forms and degrees of accountability and legitimacy for the performance of governance systems? How can mechanisms of transparency ensure accountable and legitimate earth system governance? What institutional designs can produce the accountability and legitimacy of earth system governance in a way that guarantees balances of interests and perspectives?